1. Field of the Invention
The present invention relates to a shock wave medical treatment apparatus for treating an object to be treated inside a patient, such as a cancer cell or concretion, by disintegrating them by means of the focusing energy of a shock wave.
2. Description of the Background Art
An example of a conventional shock wave medical treatment apparatus, an ultrasonic wave applicator disclosed in Japanese Patent Application Laid Open No. 62-049843 (1987), is shown in FIG. 1.
This ultrasonic wave applicator 1 comprises a concave oscillator 2 of 10 cm diamter and a constant curvature for generating focused ultrasonic waves which has an aperture of a prescribed shape at its middle, a backing material 3 uniformly attached to a back of this concave oscillator 2, an imaging ultrasonic wave probe 4 for taking images of region to be treated by transmitting and receiving imaging ultrasonic waves, which is fixed at the aperture of the concave oscillator 2 and which is a sector scanning type having an array 4a of minute oscillator elements at a bottom face, and an acoustic coupler 5 for propagating the focused ultrasonic waves from the concave oscillator 2 to a surface 32S of a patient which is made of a bag 6 of thin film having an acoustic impedance substantially equal to that of water and which is filled with water.
In this ultrasonic wave applicator 1, the array 4a of the oscillator elements of the imaging ultrasonic wave probe 4 is either aligned with a curved ultrasonic wave generating surface of the concave oscillator 2 or placed further away from the surface 32S of the patient than the curved ultrasonic wave generating surface of the concave oscillator 2.
In such a configuration, the imaging ultrasonic waves to be transmitted and received by the imaging ultrasonic wave probe 4 inevitably suffer from scattering and dissipation due to the intervening water inside the acoustic coupler 5 and the thin film of the bag 6. For this reason, the images to be displayed by a display unit (not shown) are influenced by noise so that locating the object to be treated becomes difficult.
On the other hand, an alternative configuration for the ultrasonic wave applicator is shown in FIG. 2.
This ultrasonic wave applicator 7 comprises a concave oscillator 9 for generating ultrasonic waves of focusing trajectory 12 which is similar to the concave oscillator 2 of the previous example described above and which is located below a bed 8, a water bag 10 filled with water for transmitting the ultrasonic waves which is provided between an ultrasonic wave generating surface of the concave oscillator 9 and an opening 13 of the bed 8 located above the concave oscillator 9, and a mechanical probe 11 placed inside the water bag 10 which has a fixed focal length.
In this alternative configuration, the problem of scattering and dissipation as described above for the previous example is also present. In addition, there are problems, due to the fact that the probe 11 is a mechanical probe, such as deterioration of image quality, enlargement of the configuration, and vulnerability to vibrations. Moreover, in the configuration of FIG. 2, operation of the ultrasonic wave applicator 7 is harder because this ultrasonic wave applicator 7 is fixed to the bed 8.
To deal with such problems of a conventional shock wave medical treatment apparatus, the present inventor has proposed a shock wave applicator comprising a shock wave transducer for generating shock waves with a focal point located inside a patient, a water bag provided at a shock wave generating surface of the shock wave transducer, and an imaging ultrasonic transducer located between the shock wave generating surface and the focal point for taking image data of the patient in a region including the focal point in a state of contacting its ultrasonic wave transmitting and receiving surface to a surface of the patient, as disclosed in Japanese Patent Application Laid Open No. 62-290158 (1987).
Now, in general, the distance from a body surface to the object to be treated varies according to the organ containing the object to be treated and depending on whether the patient is an adult or child. Moreover, dissipation of the ultrasonic wave varies, depending on the physical constitution of the patient.
For these reasons, there arises a necessity to change the imaging ultrasonic wave probe to that of different characteristics in accordance with the distance of the object to be treated from the body surface and the physical constitution of the patient.
However, exchangeability of the imaging ultrasonic wave probe has not been considered in the conventional shock wave medial treatment apparatus, so that the imaging ultrasonic wave probe could not be easily changed.